LOAMY BOTTOM
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition 1A More details
- Transition 2A More details
- Restoration pathway 3A More details
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
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Description
The Reference State 1.0 represents the natural range of variability under pristine conditions. The reference state has three general community phases: a shrub-grass dominant phase, a perennial grass dominant phase, and a shrub dominant phase. State dynamics are maintained by interactions between climatic patterns and disturbance regimes. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups, low fine fuel loads, and retention of organic matter and nutrients. Plant community phase changes are primarily driven by fire, periodic drought, and/or insect or disease attack.
Submodel
Description
This state is similar to the Reference State 1.0 with the same three general community phases. Ecological function has not changed, however the resiliency of the state has been reduced by the presence of invasive weeds. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups, fine fuel loads within the range of site variability and retention of organic matter and nutrients. Positive feedbacks decrease ecosystem resilience and stability of the state. These include the non-natives’ high seed output, persistent seed bank, rapid growth rate, ability to cross pollinate and adaptations for seed dispersal. Additionally, the presence of highly flammable, non-native species reduces State resilience because these species can promote fire where historically fire has been infrequent leading to positive feedbacks that further the degradation of the system.
Submodel
Description
This state has one community phase: a big sagebrush-dominated phase likely with a significant component of rabbitbrush. This state is a product of many years of heavy grazing during periods harmful to perennial bunchgrasses and/or hydrologic modification resulting in a lowered water table. Povertyweed and non-native species may become the dominate understory. The shrub overstory dominates site resources such that soil water, nutrient capture, nutrient cycling and soil organic matter are temporally and spatially redistributed.
Submodel
Mechanism
Trigger: This transition is caused by the introduction of non-native annual or perennial species, such as cheatgrass, mustard (Descurainia sp.), hoary cress, scotch thistle and bull thistle.
Slow variables: Over time, the non-native plants will increase within the community decreasing organic matter inputs from deep-rooted perennial bunchgrasses resulting in reductions in soil water availability for perennial bunchgrasses.
Threshold: Any amount of introduced non-native species causes an immediate decrease in the resilience of the site. Non-native species cannot be easily removed from the system and have the potential to significantly alter disturbance regimes from their historic range of variation.
Mechanism
Trigger: Inappropriate, long-term grazing of perennial bunchgrasses during growing season would favor shrub growth and establishment. Alteration in the hydrology of the site may also cause an increase in sagebrush; with gullying of floodplain surface the seasonally high water table is dropped and may cause a decrease in perennial bunchgrasses. Community Phase 3.1.
Slow variables: Long term decrease in deep-rooted perennial grass density resulting in a decrease in organic matter inputs and subsequent soil water decline.
Threshold: Loss of deep-rooted perennial bunchgrasses changes spatial and temporal nutrient cycling and nutrient redistribution, and reduces soil organic matter. Loss of seasonally high water table.
Mechanism
Brush management such as mowing, coupled with seeding of basin wildrye. May be coupled with restoration of the water table where gully formation has occurred. Engineered structures or low-tech process based restoration may be required. See USDA, NRCS National Engineering Handbook and Wheaton et al. 2019.
Model keys
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Ecological sites
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The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.